A visit by Russia's prime minister to Beijing ended Friday with a joint pledge of possible cooperation in space exploration, but no agreement on a pipeline sought by China to supply Siberian oil for its energy-hungry economy.

A declaration by Russian Prime Minister Mikhail Fradkov and his Chinese counterpart, Wen Jiabao, called for the two sides to increase trade and collaborate in developing nuclear power plants and natural gas. They said exports of Russian oil to China by rail should nearly double next year, to at least 105 million barrels. Wen described Chinese-Russian ties as enjoying their "best period in history," China's official Xinhua News Agency said.

But there was no indication of a deal on a planned pipeline to export Siberian oil to the Pacific coast. Beijing is lobbying Moscow to commit to building a branch to deliver some of that crude to China. The proposed US$10 billion (Ђ7 billion) pipeline has been delayed by uncertainty over its route and possible ecological impact.

Ties between Beijing and Moscow, former Cold War enemies, have flourished since the Soviet collapse. They are motivated in part by a desire to counterbalance what both sides see as U.S. dominance of global affairs. China has become the biggest foreign customer for Russia's weapons industry, and Beijing is eager to secure oil and gas from Russian fields for its booming economy.

The declaration issued Friday also said the two sides agreed to "explore the possibility for moon and deep space exploration," according to Xinhua. Russia sold China the technology that formed the basis of its manned space program, which launched a two-man crew last month on its second successful orbital mission, AP reports.